Ion transport and conduction processes in single cell membrane preparations from epithelial, nerve, muscle and secretory tissues will be studied by advanced quantitative measurements of the kinetic and stochastic phenomena that are necessary to understand physiological functions in these tissues. The control of Na and K permeability by intracellular Ca++ and H+ ions will be examined in isolated patches of apical and basolateral membrane from a kidney cell line in tissue culture. The way in which H+ affects ouabain-sensitive fluxes and its effect on the kinetics of the Na pump will be determined by flux measurements in dialyzed squid axon. The exocytosis process in secretory cells will be characterized by membrane capacitance changes related to vesicle fusion and by transient potentials and altered membrane properties connected with release. The origin of anomalous K current rectification in molluscan neurons will be studied by relaxation, fluctuation and single channel current measurements to determine whether rectification arises from voltage-dependent channel lifetimes or a nonlinear single channel conductance. Ion channel properties that account for delayed, outward K current rectification and are responsible for control of repolarization of the cardiac action potential will be measured and described in single cardiac cells from bullfrog atria. The sequence of activation of Ca channels will be examined in snail neurons and PC-12 cells. The relative effects of potential and Ca current upon inactivation will be studied. Conduction in open channels and regulation of the numbers of functional channels will also be investigated. Patch and whole cell voltage clamp methods will be used. The transmembrane ionic current generated by the Na/K ATPase in isolated frog cardiac cells will be characterized in both atrial and pacemaker cells. Voltage-dependent ion conductances will be identified in hippocampal pyramidal neurons of guinea pig and the action of acetylcholine, noradrenaline, dopamine on the conductances determined. Synaptic effects in a cultured sympathetic cell line (NG108) will be evaluated using complex impedance measurements from the soma and dendritic regions.